Effects of heavy metals

1. Effects of heavy metals and
radiation pollution on
biological system
LECTURE

2. Metals
 Metals are natural constituents that exist in the ecosystem.
 They are substances with high electrical conductivity which voluntarily lose
their electrons to form cations.
 Metals are found all over the earth including the atmosphere, earth crust,
water bodies, and can also accumulate in biological organisms including
plants and animals.

3. Heavy Metals
 Heavy metals are well-known environmental pollutants due to their
toxicity, persistence in the environment, and bio accumulative nature.
 Among the 35 natural existing metals, 23 possess high specific density
above 5 g/cm3 with atomic weight greater than 40.04 and are generally
termed heavy metals
 This category of metals termed heavy metals have not only been known for
their high density but most importantly for their adverse effects to the
ecosystem and living organisms.

4. Metals Essentiality for life
 Some of these heavy metals such as cobalt, chromium, copper, magnesium,
iron, molybdenum, manganese, selenium, nickel and zinc are essential
nutrients that are required for various physiological and biochemical
functions in the body and may result to deficiency diseases or syndromes if
not in adequate amounts but in large doses they may cause acute or chronic
toxicities.

5. Environmental pollution due to heavy
metals
 Environmental pollution is one of the major challenges in the modern
human society.
 Environmental contamination and pollution by heavy metals is a threat to
the environment and is of serious concern.
 Rapid industrialization and urbanization have caused contamination of
the environment by heavy metals, and their rates of mobilization and
transport in the environment have greatly accelerated since 1940s

6. Sources of heavy metals
Their natural sources in the environment include
 Weathering of metal-containing rocks
 volcanic eruptions
Principal anthropogenic sources include
 Industrial emissions,
 Mining,
 Smelting, and
 Agricultural activities like application of pesticides and phosphate
fertilizers.

8. Essentials and Non essential heavy metals
 Essential heavy metals are important
for living organisms and may be
required in the body in quite low
concentrations.
 Examples of essential heavy metals are
Mn, Fe, Cu, and Zn.
 Micronutrients or trace elements for
plants.
 For growth and stress resistance.
 For biosynthesis and function of different
biomolecules.
 Nonessential heavy metals have no
known biological role in living
organisms.
 Heavy metals Cd, Pb, and Hg are toxic
and are regarded as biologically
nonessential.

9. Most Hazardous Heavy Metals
 Heavy metals are among the most investigated environmental pollutants.
Almost any heavy metal and metalloid may be potentially toxic to biota
depending upon the dose and duration of exposure.
 Many elements are classified into the category of heavy metals, but some
are relevant in the environmental context.
 List of the environmentally relevant most toxic heavy metals and
metalloids contains Cr, Ni, Cu, Zn, Cd, Pb, Hg, and As.
 Heavy metal pollutants most common in the environment are Cr, Mn, Ni,
Cu, Zn, Cd, and Pb

10. Chromium Cr
Man Made Sources
The anthropogenic sources of Cr include
 Electroplating industries
 Leather tanneries
 Textile industries
 Steel industries
Natural Sources
Globally, about 50,000 t/year of Cr may be
emitted from
 Coal combustion
 Wood burning
 Refuse incineration
 Fertilizers also usually contain significant
contents of Cr.

11. Cadmium Cd
Man-Made Sources
An anthropogenic source is
 Nonferrous metal mining (especially
processing of Pb-Zn ores).
 Globally 7,000 t/year of Cd may be emitted
from coal combustion,
 Sewage sludge incineration is also a source
of Cd.
Natural Sources
The natural sources of Cd in the environment
are
 Volcanic action
 Weathering of rocks

12. Lead Pb and Nickel Ni
Lead
Pb is released to the environment from
different sources including
 Acid batteries,
 Old plumbing systems
 Lead shots used for hunting of game birds.
 Combustion of leaded gasoline is also a
source of Pb in the environment.
 Tetraethyl lead as an antiknock agent
Nickel
 Globally, about 60,000 t/year of Ni may be
generated from
 Coal combustion
 Its greater portion remains in the ash

14. Contamination of water
 It is said that water is the “life-blood of the biosphere.” Since water is a
universal solvent, it dissolves different organic and inorganic chemicals and
environmental pollutants.
 Aquatic ecosystems, both freshwater and marine, are vulnerable to
pollution.
 Contamination of water resources by heavy metals is a critical
environmental issue which adversely affects plants, animals, and human
health.
 Heavy metals are extremely toxic to aquatic organisms even at very low
concentrations . These elements can cause significant histopathological
alterations in tissues of aquatic organisms such as fish.

15. Contamination of water
 Aquatic ecosystems are contaminated by heavy metals from different
sources.
 One source of heavy metals in the aquatic ecosystems is effluents from
mining operations.
 Other sources of water contamination with heavy metals include different
industrial effluents, domestic sewage, and agricultural run-off.
 The release of industrial effluents without treatment into the aquatic
bodies is a major source of pollution of surface and groundwater water.
 Pollution of water bodies with heavy metals is a worldwide problem
because of the environmental persistence, bioaccumulation, and bio
magnification in food chains and toxicity of these elements

16. Contamination of soil
 Heavy metals and metalloids are released into soils from the parent
material (lithogenic source) and different anthropogenic sources.
 Factors affecting the presence and distribution of heavy metals in soils
include composition of parent rock, degree of weathering, and physical,
chemical, and biological characteristics of soil and climatic conditions.
 Significant enrichment of heavy metals has been reported in soils receiving
more input of fertilizers and Cu fungicide compared to virgin soils and soils
receiving low inputs

17. Contamination of soil
 In urban areas, soils may be contaminated with heavy metals from heavy
vehicular traffic on roads.
 Soil samples in urban areas have elevated concentrations of Pb, out of
which 45–85% is bioaccessible.
 The bioavailability of heavy metals in soils is very important for their fate in
the environment and for their uptake in plants.
 Different heavy metals have different bioavailabilities in soils, and this
bioavailability is dependent on metal speciation and on different
physicochemical properties of soils.

19. Trophic transfer of heavy metals

20. Health effects of heavy metals toxicity in
humans
 Heavy metal toxicity can have several health effects in the body.
 Heavy metals can damage and alter the functioning of organs such as the
brain, kidney, lungs, liver, and blood.
 Heavy metal toxicity can either be acute or chronic effects.
 Long-term exposure of the body to heavy metal can progressively lead to
muscular, physical and neurological degenerative processes that are similar
to diseases such as Parkinson’s disease, multiple sclerosis, muscular
dystrophy and Alzheimer’s disease

21. Heavy Metals Toxicity

22. Diseases

24. Radiations
 Radiation is energy given off by matter in the form of rays or high-speed particles.
All matter is composed of atoms. Atoms are made up of various parts;
the nucleus contains minute particles called protons and neutrons, and the atom's
outer shell contains other particles called electrons. The nucleus carries a positive
electrical charge, while the electrons carry a negative electrical charge. These forces
within the atom work toward a strong, stable balance by getting rid of excess atomic
energy (radioactivity). In that process, unstable nuclei may emit a quantity of
energy, and this spontaneous emission is what we call radiation

26. Radiation
 Radiation is energy that comes from a source and travels through space at the speed
of light. This energy has an electric field and a magnetic field associated with it, and
has wave-like properties. You could also call radiation “electromagnetic waves”.

27. Radioactive
 Large unstable atoms become more stable by emitting radiation to get rid of excess
atomic energy (radioactivity). This radiation can be emitted in the form of positively
charged alpha particles, negatively charged beta particles, gamma rays, or x-rays, as
explained below.
 Radioactive decay — radioisotopes lose their radioactivity over time.
 This gradual loss of radioactivity is measured in half-lives.
 Essentially, a half-life of a radioactive material is the time it takes one-half of the
atoms of a radioisotope to decay by emitting radiation.

28. Non ionizing
 Radiation can be either ionizing or non-ionizing, depending on how it affects
matter.
 Non-ionizing radiation includes visible light, heat, radar, microwaves, and radio
waves.
 This type of radiation deposits energy in the materials through which it passes, but
it does not have sufficient energy to break molecular bonds or remove electrons
from atoms.

29. Ionizing
 By contrast, ionizing radiation (such as x-rays and cosmic rays) is more energetic
than non-ionizing radiation.
 Consequently, when ionizing radiation passes through material, it deposits enough
energy to break molecular bonds and displace (or remove) electrons from atoms.
 This electron displacement creates two electrically charged particles (ions), which
may cause changes in living cells of plants, animals, and people.

30. Sources
 Radon
 Carbon and potassium
 Rocks and Soils
 The Sun

31. Impacts on health
 Radiation is a mutagen, which eventually can lead to cancer.
 Radiation can either kill cells or damage the DNA within them, which damages their
ability to reproduce and can eventually lead to cancer.
 When radiation is present, high energy particles pass through your body.
 These can collide with atoms in your body and disrupt atomic structure.
 Atoms make up your DNA, so over time, your DNA can be damaged.
 Often, it is the replication mechanisms of cells that is damaged, so uncontrolled cell
division occurs- which is the definition of cancer.